Great Basin scientists unleash new weapons to fight invasive cheatgrass
This guy is lovely!" ecologist Beth Leger exclaims, falling to her knees. A tiny, energetic woman in her mid-30s, Leger hovers, bee-like, over a teensy grass with blue-green blades. It is, she tells me, a "cute" native called Poa secunda.
It's early May, and Leger, graduate student Owen Baughman and I are crouched on Peavine Mountain, a scrubby rise near the University of Nevada, Reno, where she is an associate professor of plant ecology. The ground around us is covered with the invasive annual Bromus tectorum, also known as cheatgrass. This is not surprising; the Great Basin is a disturbed landscape, and cheatgrass is now its dominant inhabitant. Around the little Poa though, there is no cheatgrass at all, just a foot of bare, pebbly dirt. "We did some trials to see what native perennials were the most competitive with cheatgrass, and it was this guy," says Leger.
Leger scoops away the soil around its base, digging carefully underneath it. "I don't want to kill him, but it's instructive to do that because his roots are super fine and they go out really shallowly, all through this area," she explains, gesturing at the bare circle. "Cheatgrass (also) has super-fine roots and this is about the only native plant I've ever seen that has the same sort of roots." That allows the Poa to take up space and use nutrients the weedy invader would typically claim. Determined to show me its root structure, Leger finally pulls the demonstration plant out of the ground, sacrificing it for the sake of knowledge. "Sorry, dude," she tells the grass. "You'll be famous."
The ancestors of Leger's beloved Poa first encountered cheatgrass, a native to parts of Europe and Asia, in the late 1800s. Western settlement had brought widespread livestock grazing to the Great Basin, a Texas-sized area that covers 180 million acres in southeastern Oregon, southern Idaho, western Utah and Nevada. That was a shock to native bunchgrasses like Poa and Indian ricegrass, which, in that part of the West, had evolved in an environment unused even to bison. Cheatgrass seized its opportunity. The weed hitchhiked from Europe in contaminated seed, straw and ship ballast, and crisscrossed the West with the railroads, which spread it with the straw used for livestock. By 1930, cheat was everywhere. As Aldo Leopold wrote in the 1949 classic A Sand County Almanac, "One simply woke up one fine spring to find the range dominated by a new weed."
That new weed would drastically change the region's fire ecology, among other things. In a typical Great Basin shrubland, forbs and grasses grow patchily underneath a canopy of well-spaced shrubs like sagebrush and shadscale. In contrast, cheatgrass masses in a smothering mane. Its survival strategy is to beat out other plants, Red Army-like, through its sheer numbers: It can drop 50,000 seeds per square meter. An annual, it dies off every year, leaving a thick thatch of flammable material. Even the smallest spark can set off fast-moving fires that kill off any remaining native shrubs. Then, next growing season, those millions of cheatgrass seeds outcompete any surviving natives. After the first burn or two, the fire cycle is forever changed. Normal fire frequency in the Great Basin is every 30-70 years; cheatgrass monocultures burn every three to 10. The bare soil left after fire can blow away in spring and land on snow in far-away mountains, causing quicker melt-off. With nowhere to hide and no shrubs to browse or nest in, wildlife -- including mule deer and the imperiled sage grouse -- quickly move out.
For many years, the Bureau of Land Management, which manages much of the land in the Great Basin, more or less ignored cheatgrass. In the mid-1980s, though, a number of large fires swept through sagebrush communities, and land managers began investigating how to protect and restore the habitat. Then, in the summer of 1999, the Great Basin burned as never before, with fires marching across almost 2 million acres. That forced the agency to take a more aggressive approach to fighting cheatgrass. Yet so far, many restoration efforts have come up short, as native soil erodes after fires, planted seeds fail to establish, and cheatgrass returns en masse. Today, ecologists estimate that it has expanded to between 20 to 50 million acres in the region, and forms a near monoculture in at least 10 to 12 million of those acres.
Cheat isn't even the worst thing that could happen to the Great Basin. Now that the ecosystem is essentially shattered, new invaders have an easier time moving in. Plants like medusahead wildrye, thistles and knapweed lurk in the wings. Unless cheat-altered landscapes can be made more resilient, one of these may become the next great invader, says Mike Pellant, a rangeland ecologist who coordinates the BLM's Great Basin Restoration Initiative. And, Pellant warns, "we don't know which one and where and how fast. So if you think of a downward spiral, cheatgrass is not the bottom of the ecological barrel in the Great Basin."
That's the dark side, he says. "The bright side is we've got great scientists working on the problem." Of course, even the best science can't give the BLM the ability to treat 50 million acres of invaded land, especially when funding for reseeding comes primarily in a reactive rather than proactive form, tied to post-fire restoration. Pellant says any efforts to fight cheat will be mostly focused in sensitive places like wilderness study areas and important sage grouse habitat. A silver lining to the bird's decline is the federal money dedicated to keeping it off the endangered species list, which enables the agency to do more restoration.
Those priority areas can use any help that Leger, and her cheatgrass-fighting native plants, can give. And she's not alone; the effusive scientist is working alongside an Avengers-like posse of restoration scientists, all raring to put into practice new knowledge about the best way to fight Great Basin cheatgrass.
In her U.S. Forest Service laboratory in Provo, Utah, ecologist Susan Meyer wends through piles of petri dishes. Each holds a fungus she calls the Black Fingers of Death, which grows on cheatgrass seeds, poking out like grasping fingers. Aptly named, it has the power to mass-murder those seeds.
Meyer discovered this power while trying to solve a restoration problem. Typically, after a fire, teams would spray a pre-emergent herbicide in the fall, to kill cheatgrass when it sprouted after autumn rains. At the same time, they'd seed natives to sprout the following year, after the cheatgrass was killed off.
But the grass is clever; not all its seeds germinate with that first rainfall, and the leftovers, often as many as 10,000 per square meter, go dormant, usually until the rains of the following fall. By then, the herbicide is gone, and spraying again isn't possible, because it would kill germinating natives. "It's common to have a reasonably successful seeding that then gets overwhelmed by cheatgrass the next year," because of those second string germinators, says Meyer.
But Meyer's fieldwork also showed her that some of those second-year seedlings were dying off, even without herbicide. "We found this fungus that was eating 60 to 90 percent of the seeds."
That fungus, which hitched a ride across the ocean attached to cheatgrass, was Black Fingers of Death, or BFOD. In its natural state, BFOD is not potent enough to kill all the late germinating seeds. Meyer thought she could get around that by seeking out the most deadly strains and culturing them, so that all those late-germinating cheatgrass seeds "won't be there next year to haunt your seeding." Meyer's achieved a pretty consistent 90 percent seed death rate, with 100 percent in a few cases. She has applied for a patent, and has been contacted by a couple of biocontrol companies.
In order to make Black Fingers as deadly as possible, Meyer's collaborators have gone so far as to change how it reproduces. In the lab, it typically does this clonally, but biologist Julie Beckstead is working on getting the fungus to "do sex," says Meyer, which would allow the researchers to breed the most effective BFOD strains together.
When used in concert with an herbicide that takes out the first-year crop of cheatgrass seedlings (because they germinate so quickly, the fungus doesn't work on those early seeds, although Meyer is researching that problem), Meyer's work may create the perfect conditions for restoration. She's tested to see if it kills native grasses, and has found little evidence that it would affect them.
There is a catch, though. Even if a biological control like Meyer's succeeds, land managers are still left with an open desert landscape. It's up to her fellow scientists to keep cheatgrass -- or something worse -- from seizing the moment yet again.
Lack of rain is the main culprit in most Great Basin restoration failures. A wet year makes everyone a good range manager, as the saying goes. Yet even though land managers know their seedings fail more often in tough, dry years, they do not know exactly why. Jeremy James, a range ecologist with the University of California Agriculture and Natural Resources Program, reasoned that if he knew exactly what caused plants to die, he could help them survive.
In 2007, James experimented with tracking seeds planted after four different fires in Great Basin ecosystems in eastern Oregon. To his surprise, the ecologist found that it wasn't that seeds failed to germinate. "In most years, we can get 60, 70, 80 percent germination in the field," says James. "But we also found that about 90 percent of those seeds that have initiated germination never make it. They never actually get above the soil surface."
To understand the many ways seeds can germinate but still fail, think about Beth Leger's Poa. Say one of its seeds drops down onto that hard pebbly dirt and makes its way into the soil. Come spring, the 3.5 millimeter oblong kernel might swell with water as the ground warms and snow melts. Then it stretches out its first root, and sends the beginnings of a leaf upward, towards the soil surface. But in a light snow year, the seed may stop there, lacking the moisture to continue. Maybe there's a late hard frost, and the tiny root freezes and withers. Perhaps a fungus in the soil devours the seed, or the seedling simply cannot push its way through the hard, dry soil crust.
In a normally functioning ecosystem, none of these failures would really bother the Poa. Sure, its seeds might not make it one year, but they'd succeed the next, or the one after that. But while Poa might not be in a hurry, rangeland managers lack the luxury of time. They need natives to establish quickly, before cheatgrass takes over again.
In James' next experiment, a three-year study that he is conducting with Leger and a few other scientists, he will try to narrow down the causes behind seed failure. What he finds could radically change BLM practices after a fire. If those native seeds are mostly becoming pathogen fodder, the BLM could order seed coated in fungicides. If the problem is lack of moisture, seeds could perhaps be planted to have better seed-soil contact, especially in dry years. James' colleague, ecologist Matthew Madsen, has been working on a technique called "bundling," where many native seeds are coated and clustered together, like clumps of granola. In his trials, this has helped them retain moisture, emerge through thick soil crusts and better survive dry winters.
James is also working with a plant physiologist and modeler, Stuart Hardegree of the USDA Agricultural Research Service in Boise. The models Hardegree is developing, based on historic weather patterns, will help land managers predict weather conditions months into the future. That way they'll know, when seeding after a fire, if they should give seeds extra help, depending on whether that spring will be drier or colder. In some cases, if the model is pessimistic about restoration conditions, land managers might elect to plant something like crested wheatgrass, which is more successful at establishing than native plants, says Hardegree. Even planting a field of non-native crested wheatgrass might be better than doing an expensive seeding of natives and having them fail, followed by a return to flammable cheatgrass.
"Ugh, it's so depressing." Beth Leger is tromping through a golden-thatched valley in northwestern Nevada near the town of Winnemucca. It's full of dried cheatgrass. As a chill wind whips our clothes, our eyes comb the ground, searching for plants other than cheat. "It's remarkable to me that there can be this little diversity," sighs Leger. She's surprised, too, because although it's common to think of fields of cheatgrass as devoid of any other species, her research has found otherwise.
When Leger first came to Reno, like most restoration scientists, she viewed cheatgrass-invaded landscapes as monocultures, where native plants no longer existed. Yet one day, exploring nearby Peavine Mountain, Leger noticed a sprinkling of native grasses among the weeds. She wondered if they'd be useful for restoration, since they must have adapted somehow in order to fight off the weed and survive. So she waded out into a cheatgrass sea, dug up a few native plants, and started conducting experiments.
Leger collected natives from cheat-covered areas and natives from more intact ecosystems, planted them alongside cheatgrass, and measured how they grew. "It's kind of like boxing. You put them in a ring and see who wins." Her early results were impressive. A number of plants from the weedy areas suppressed the growth of cheatgrass and were also able to successfully reproduce.
"A native plant! I found one native plant!" shouts Leger. Kneeling, the ecologist grins for the first time since our arrival in the cheatgrass sea. "It's a Lomatium. In terms of its restoration potential I don't think it's really one of the big players for competing with cheatgrass, but in terms of diversity it's good."
Back at her University of Nevada test plots, Leger has experimented to pinpoint the most competitive natives. She takes me to a dry field surrounded by fencing, where a few green plants have a foothold. "This is squirreltail," she says, pointing out plants that have proven to outcompete cheatgrass. "Amsinckia is one, Mentzelia, this is a lovely one, pretty big after fires."
Leger calls the Amsinckia a "weedy native," because it likes disturbed sites. Her test plots have largely failed this year due to lack of rain, but a few plucky Amsinckias persisted. Last year, when Leger experimentally planted Amsinckia near cheatgrass, the native reduced the weed's size by 97 percent and suppressed its seed production from 576 seeds per plant to just 76.
In a natural succession scenario, Amsinckia and other weedy natives would be some of the first plants to colonize a burned or disturbed area. But plants like Amsinckia have seldom been included in restoration seed mixes, partly because they are toxic to cattle, and partly because managers have wanted to seed plants like sagebrush that would be found in a mature Great Basin plant community. If Amsinckia were used in restoration, though, Leger believes it could truly act like a colonizer. It would fight off cheatgrass, but only stick around for a couple years. That would give some time for other perennial natives like squirreltail or Poa to establish, after which they can also do their part fending off cheatgrass.
Leger sees her and James' work as complementary to what Meyer is doing with Black Fingers of Death. "If you could knock this whole (cheatgrass) seed bank down by 90 percent (with BFOD) and could put some plants in there that could just survive for that first year, the next year might be awesome."
As Leger and I crunch through the patch of dead cheatgrass outside Winnemucca, the ever-present wind stiffens and the sky grays. The effusive scientist's optimism falters slightly, as she ponders the magnitude of the problem. "The scale of this is ridiculous. This is just one little spot. Think about how many native seeds would need to be planted here. It's unbelievable. And we don't even have a recipe (for restoration). So our hope is that we can find a recipe."
That recipe might go something like this: October comes, and a specially modified drill seeder trundles across the thatch, planting fungicide-coated Poas, Amsinckias, and squirreltails -- the tough ones Leger bred from her collections -- at depths where they are more likely to succeed in the upcoming dry winter. Soon after, a plane flies over, dropping herbicide for the early cheat seeds and granules of death-dealing Black Fingers for the later ones. In a few years, small sagebrush are sprouting, Indian ricegrass reappears, and latecomer perennials like larkspur and penstemon start to make a comeback. The next fire to sweep through doesn't come for 20 more years, and by that time, enough native seeds have dropped in the soil that plants regenerate on their own, or with only a little human help. Leger, I think, imagines this too, but her hope is somewhat tempered.
"You look at this place and you can see very realistically: We could still fail. But I think we at least need to try some of those more carefully designed ways. And then if we still fail, I think we need to stop. But I'm not ready to stop trying."
This story was funded by a Fund for Environmental Journalism Grant from the Society of Environmental Journalists.